1. Field of the Invention
The present invention relates to a liquid crystal display apparatus, and more particularly to a LCD (Liquid Crystal Display) capable of automatically adjusting a driving voltage according to an amount of emitted light.
The present application is based on Korean Patent Application No. 2002-30252, filed May 30, 2002, which is incorporated herein by reference in its entirety
2. Background of the Related Art
Recently, as mobile devices such as PDAs (Personal Digital Assistant), palm-top computers and cellular phones came into general use, LCOS (Liquid Crystal on Silicon) displays developed as microdisplay apparatuses for the mobile devices.
A color sequence of R+(Red), G+(Green), B+(Blue), W+(White), R−(Red), G−(Green), B−(Blue), W−(White) is displayed on a frame of the LCOS display in accordance with a predetermined timing.
Since transmittance characteristics are different with respect to different wavelengths of the R, G, B colors, an optimal voltage has to be set for each of the color wavelengths in order to optimize a color setting of the LCOS display.
Therefore, a different voltage of R+, G+, B+, Black+, White+, R−(Red), G−(Green), B−(Blue), W−(White) needs to be inputted to each frame.
The LCOS display needs individual power sources for normally black operation and for normally white operation.
FIG. 1 is a schematic diagram showing a circuit for generating a Vcom (Common Electrode Voltage) for a conventional LCOS display.
The circuit for generating the Vcom voltage comprises a power source unit 10, a multiplexer 20 and a buffer 30.
The power source unit 10 includes a plurality of adjustable resistors R1 to Rn corresponding to the individual power sources needed for the LCOS display. The adjustable resistors R1 to Rn are individually set to output different voltages ranging from −5.2V to 5.2V. The multiplexer 20 outputs the voltages inputted from the power source unit 10 to the buffer 30 in accordance with 4 bit selection signals a, b, c, and d.
In the conventional LCOS display, the Vcom voltage is adjusted by manually adjusting the plurality of adjustable resistors in accordance with a panel status. This is an inefficient process for image quality adjustment, and has lower precision as well as increased material cost.